Hi, I am a new member and this is my first posting. I have a 2004 Monte Carlo SS Supercharged that ran great before these mods. We just now put on a GMPP cat back exhaust, 1 level colder plugs(605's gapped at .55), 180 thermostat, 3.4 pulley, Thrasher CAI, and PCM tuned V.1 from 3800 performance. We just took it for a test drive and when you get on it it is breaking up all over the place, and sometimes the engine light flickers. It only happens at speeds as soon as the supercharger boost kicks in. It is very hard to explain what it is doing. Do we need to adjust anything? What is the problem? I wish I could take an audio recording and play it for someone. PLEASE HELP!

 

Sounds like you might have a misfire if the CEL is blinking on and off. I'm not much of an expert but that's my somewhat educated guess. Have you tried putting your old plugs back in?

 

It only happens at speeds as soon as the supercharger boost kicks in

 

I know going down on pulley size can cause KR issues on the L67...3.4 sounds pretty like a big jump down, you really need to be heavily modded before you start dropping pulley's.

And a flashing CEL is a misfire of somesort....You sure all your plugs are connected? Maybe one is loose?

 

You probably shouldn't have dropped a pulley size before checking for KR (Knock Retard). You also may need a down pipe with high flow cat and headers to safely run a smaller pulley in addition to the other mods you listed.

 

You are not ready to run the 3.4 pulley yet.

You are missing quite a few supporting mods, and the flashing CEL is definitely a mis-fire.

 

So if I get the downpipe and hi-flow cat , it will stop doing this? Does that replace the u-bend? I can't take the 3.4 off because all the pins broke on the pulley puller I bought from 3800performance. How can I get more of those pins? This is turning into a nightmare...if I do get the stock pulley back on do I have to take out the 180 thermostat and 605 plugs?

 

I wouldn't worry about the thermostat, but the plugs could be your problem with the misfire, are you sure they are all seated properly?

And it really isn't a matter of "what mods you need to put on first" it's all about scanning your car properly for Knock Retard, or KR. Once you get the KR to 0° at all driving, then you can drop a pulley size and work on getting that new size 0°

 

The 180 T-Stat can stay...as for the plugs, i'm not sure.

 

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